It depends on which converters they are changing out. There are four on the Armada. The primary cats are welded to the manifolds, and the entire manifold/cat assembly must be changed. Not an easy or quick job.
The secondary cats are in the "B" pipes, which are between the primary cats and the Y pipe. They are much easier to change; it should take only about an hour to change them.
Just put my baby in the shop today for service engine soon light (71k miles). Verdict-bad cat! They say it will be ready tomorrow by lunch so it must have been the secondary cats, not the primary. Dealer says it is covered under the 80k emissions warranty.
Just a little update. I just had some work on my truck (79K miles) for a noise coming from the suspension on the passengers side. My wife kept telling ,e she felt a rattling in the floorboard. So after a couple of visits, they narrowed it don and found out there was a loose bolt high up on the stabalizer bar that they found with a little rust on, indicating that it had been loose for a little while. ANYWAY, noise gone and all is good. 2 days work for $50 dollar deductable.
Service Engine Soon light came on last night (80.5K miles). So this morning on the way to work, I stopped by the dealer in Tyson's Corner, VA near my job for a diagnosis.
Low and behold, the catalytic convertor is the culprit. Thank god I have the Gold Plus warranty. It has paid for itself. They ordered the exhaust and it will be in Tuesday. I am scheduled to get it changed on Wednesday and get a loaner/rental while they finish the work. Again, it will be for $50.